U.S. patent number 7,998,241 [Application Number 12/068,093] was granted by the patent office on 2011-08-16 for method for recovering rhodium.
This patent grant is currently assigned to JX Nippon Mining & Metals Corporation. Invention is credited to Yoshio Ito, Shoujirou Usui.
United States Patent |
7,998,241 |
Usui , et al. |
August 16, 2011 |
Method for recovering rhodium
Abstract
The present invention provides a method for recovering rhodium
sponge in high yield from ammonium hexachloro rhodate solution. The
method comprises adding formic acid to ammonium hexachloro rhodate
solution to reduce the rhodate, recovering reduced rhodium as
rhodium black, and calcining the rhodium black under hydrogen
atmosphere without water-washing to obtain rhodium sponge.
Inventors: |
Usui; Shoujirou (Oita,
JP), Ito; Yoshio (Oita, JP) |
Assignee: |
JX Nippon Mining & Metals
Corporation (Tokyo, JP)
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Family
ID: |
39262666 |
Appl.
No.: |
12/068,093 |
Filed: |
February 1, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080236337 A1 |
Oct 2, 2008 |
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Foreign Application Priority Data
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Mar 30, 2007 [JP] |
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2007-090629 |
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Current U.S.
Class: |
75/392;
75/631 |
Current CPC
Class: |
C22B
5/00 (20130101); C22B 3/44 (20130101); C22B
11/042 (20130101); C22B 11/04 (20130101); C22B
11/06 (20130101); C22B 3/26 (20210501); Y02P
10/20 (20151101); C22B 3/165 (20130101) |
Current International
Class: |
C22B
61/00 (20060101) |
Field of
Search: |
;75/392,101 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 048 103 |
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Mar 1982 |
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EP |
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0 049 567 |
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Apr 1982 |
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EP |
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1-30896 |
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Jun 1989 |
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JP |
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2006-265677 |
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Oct 2006 |
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JP |
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2007-154252 |
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Jun 2007 |
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JP |
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2007-270228 |
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Oct 2007 |
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JP |
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Other References
NPL: Machine translation of JP-2006265677 Oct. 2006. cited by
examiner .
Paretsky, V.M et al. "Hydrometallurgical Method for Treating
Special Alloys, Jewelry, Electronic and Electrotechnical Scrap."
State Research Center of Russian Federation, 2004, p. 713-721.
XP009098610. cited by other.
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Primary Examiner: King; Roy
Assistant Examiner: Yang; Jie
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. A method for recovering rhodium in a yield of 98.7% or higher
comprising: adding formic acid to ammonium hexachloro rhodate
solution to reduce the rhodate, recovering reduced rhodium as
rhodium black, and; calcining the rhodium black under hydrogen
atmosphere without water washing to obtain rhodium sponge.
2. The method for recovering rhodium as claimed in claim 1, wherein
the step of calcining the rhodium black is conducted in a tube made
of alumina to prevent contamination with iron or the like.
Description
FIELD OF THE INVENTION
The present invention relates to technology for recovering rhodium
sponge from ammonium hexachloro rhodate solution in high yield by
adding formic acid to the solution to recover rhodium black, then
calcining it under hydrogen atmosphere.
BACKGROUND OF THE INVENTION
Japanese examined patent publication No. H01-30896 "Noble Metal
Extraction from Noble Metal-Containing Solution" discloses
technology for recovering rhodium as rhodium black from ammonium
hexachloro rhodate solution by adding formic acid to the
solution.
However, it does not disclose a method for obtaining rhodium sponge
from ammonium hexachloro rhodate solution in high yield.
The inventors have found out that rhodium sponge can be obtained in
high yield without sacrificing impurity level by omitting the
water-washing of rhodium black in a method for recovering rhodium
sponge from ammonium hexachloro rhodate solution comprising
reducing the rhodate with formic acid to obtain rhodium black and
then calcining the rhodium black under hydrogen atmosphere.
Problems to be Solved by the Invention
The object of the invention is to provide a method for recovering
rhodium sponge from ammonium hexachloro rhodate solution in high
yield.
Means for Solving the Problems
The inventors have made the following invention to solve the
aforementioned problem. (1) a method for recovering rhodium in high
yield comprising adding formic acid to ammonium hexachloro rhodate
solution to reduce the rhodate, recovering reduced rhodium as
rhodium black, and calcining the rhodium black under hydrogen
atmosphere without water-washing to obtain rhodium sponge having
low impurity level.
Advantageous Effect of the Invention
According to the method for recovering rhodium of the invention,
(1) rhodium can be recovered in high yield since rhodium black is
calcined without water-washing, thus preventing dissolution loss of
rhodium caused by the water-washing; (2) rhodium sponge can be
obtained having as low impurity level as in the case where
water-washing is conducted.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a process flow of an example in accordance with the
invention.
FIG. 2 shows a process flow of a comparative example.
BEST MODE FOR CARRYING OUT THE INVENTION
The invention will be explained in detail hereinafter.
A method for obtaining rhodium metal comprising adding formic acid
to ammonium hexachloro rhodate solution to reduce the rhodate,
recovering reduced rhodium as rhodium black, and calcining the
rhodium black under hydrogen atmosphere has been known. However,
hydrochloric acid and formic acid are deposited on the rhodium
black recovered by filtration from the post-formic acid reducing
solution. Therefore, when the rhodium black is calcined without any
additional process, the rhodium may be contaminated by the
corrosion of the firing furnace in case where the equipment is a
SUS-made furnace or the like. In addition, there was a concern that
chlorine might remain in the calcined rhodium. Therefore, it has
been thought that rhodium black needs to be water-washed before the
calcining.
Rhodium black in itself is not dissolved by water-washing. However,
the inventors have found out that a part of rhodium black which is
recovered by the filtration in the aforementioned method is
dissolved when it is water-washed, thereby causing a loss of
rhodium.
It is believed that re-crystallized ammonium hexachloro rhodate,
which is soluble in water, is mixed in a portion of the filtrand
and causes rhodium loss during the water-washing.
The dissolution loss of rhodium caused during this water-washing is
around 10%.
Furthermore, in the method in which rhodium black is recovered by
formic acid reduction and filtration, the rhodium loss into the
filtrate can be decreased by recovering rhodium also as ammonium
hexachloro rhodate by filtration. In this way, the dissolution loss
of rhodium due to water-washing of rhodium black can be cut to zero
by calcining rhodium black under hydrogen atmosphere without
water-washing.
In addition, although there was a concern that ammonium hexachloro
rhodate might mix in the rhodium black, thereby increasing the
impurity level of the recovered rhodium sponge if the water-washing
is omitted, it has turned out that, rhodium sponge obtained without
water-washing can have as low impurity level as in the case the
where water-washing is conducted.
There are two reasons for the result. Firstly, since the
concentration of metals other than rhodium (e.g., Pt, Pd, Ru, Ir,
Cr, Fe, Ni, Al, Cu, Pb, and Ag) contained in the solution before
the formic acid reduction is sufficiency low, i.e., equal to or
less than 1 mg/l, the amount of impurities mixed from
post-reduction solution deposited on the rhodium black is small.
Secondly, since hydrochloric acid mixed as deposited solution on
the rhodium black evaporates upon calcining at 750-850.degree. C.
under reduction atmosphere, it does not remain in rhodium
sponge.
The impurities mixed into rhodium by the corrosion of the equipment
can be prevented by using materials such as alumina in the area
where rhodium may be contaminated.
The invention will be explained in detail with reference to the
flow sheets shown in FIGS. 1 and 2. The solutions were analyzed by
an ICP emission spectroscope analyzer and the rhodium sponges were
analyzed by a glow discharge mass spectroscope for an example of
the invention and comparative examples.
EXAMPLES
Table 1 shows the composition of the Rh-containing solution used in
this example.
TABLE-US-00001 TABLE 1 Concentration mg/L Rh Pt Pd Ru Ir Cr Fe Ni
Al Cu Pb Ag 52643 <1 <1 <1 <1 <1 <1 <1 <1
<1 <1 <1
107 mL of formic acid, which corresponds to 3 reducing equivalents
with respect to Rh, was added to 1 L of the solution shown in Table
1, and the solution was heated and stirred at 90.degree. C. The
solution was allowed to cool to room temperature before it was
filtered. As a result, 99.2% of Rh was recovered as Rh black while
Rh contained in the filtrate was small and merely 0.4 g/L.
Without water washing, the Rh black was then calcined for 2 hours
at 800.degree. C. under reduction atmosphere consisting of 5%
hydrogen and 95% argon to obtain rhodium sponge. Incidentally, the
calcining was conducted in a tubular furnace made of alumina to
prevent contamination with iron or the like.
The amount of rhodium sponge recovered was 51.9 g and the yield was
as much as 98.7%. The amount of impurities was very small and
merely 162 ppm.
Table 2 shows the aforementioned values.
TABLE-US-00002 TABLE 2 post-reduction post-reduction recovered
filtrate filtrate Rh sponge total impurity Rh amount in pre- Rh
amount water-washing of Rh amount weight concentration reduction
solution (g) (g) yield (%) Rh black (g) yield (%) (g) yield (%) in
Rh sponge Example of the 52.6 0.4 0.8 no 0 0 51.9 98.7 162
invention Comparative 52.6 0.4 0.8 yes 2.7 9.5 46.8 89.0 204
Example
Table 3 shows the composition of the impurities.
TABLE-US-00003 TABLE 3 Example of the Comparative invention Example
without water- purified water atomic washing of Rh repulping of Rh
number black black 3 Li <1 <1 4 Be <1 <1 5 B <1
<1 11 Na 2 <1 12 Mg 2 <1 13 Al 17 16 14 Si 29 67 15 P 1 2
16 S <1 <1 17 Cl 6 4 19 K <1 <1 20 Ca 4 1 21 Sc <1
<1 22 Ti <1 <1 23 V <1 <1 24 Cr 17 <1 25 Mn <1
<1 26 Fe 4 7 27 Co <1 <1 28 Ni <1 <1 29 Cu 22 29 30
Zn <1 <1 31 Ga <1 <1 32 Ge <1 <1 33 As <1
<1 34 Se <1 <1 35 Br <1 <1 37 Rb <1 <1 38 Sr
<1 <1 39 Y <1 <1 40 Zr 8 <1 41 Nb <1 <1 42 Mo
<1 <1 44 Ru 6 8 45 Rh <1 <1 46 Pd <1 <1 47 Ag
<1 <1 48 Cd <1 <1 49 In <1 11 50 Sn <1 <1 51
Sb <1 2 52 Te 35 46 53 I <1 <1 55 Cs <1 <1 56 Ba
<1 <1 lanthanide <1 <1 series 72 Hf <1 <1 74 W
<1 <1 75 Re <1 <1 76 Os <1 <1 77 Ir <1 <1
78 Pt 9 11 79 Au <1 <1 80 Hg <1 <1 81 Tl <1 <1 82
Pb <1 <1 83 Bi <1 <1 90 Th <1 <1 92 U <1 <1
total amount of 162 204 impurities (ppm) Rh amount (%) 99.984
99.980
Comparative Example 1
107 mL of formic acid, which corresponds to 3 reducing equivalents
with respect to Rh, was added to 1 L of the solution shown in Table
1, and the solution was heated and stirred at 90.degree. C. The
solution was allowed to cool to room temperature before it was
filtered. As a result, 99.2% of Rh was recovered as Rh black while
Rh contained in the filtrate was small and merely 0.4 g/L.
After that, the Rh black was washed with water.
In this process, the Rh loss into the filtrate was 2.7 g/L, i.e.,
9.5%. After the water-washing, the Rh black was calcined for 2
hours at 800.degree. C. under reduction atmosphere consisting of 5%
hydrogen and 95% argon to obtain rhodium sponge.
The amount of rhodium sponge recovered was 46.8 g and the yield was
89.0%, substantially lower than the example of the invention. The
amount of impurities was 204 ppm and substantially the same level
as in the example of the invention.
Table 2 shows the aforementioned values.
Table 3 shows the composition of the impurities.
Comparative Example 2
When the calcining was conducted under the same condition as in the
example of the invention except that a SUS-made tube was used, the
rhodium sponge contained 40 ppm of iron, and a desired product
could not be obtained.
* * * * *